Tissue and other body structures may be protected using a hydrated composition made from free-flowing rehydratable particles or a rehydratable sponge comprising substantially collagen-free dehydrothermally crosslinked thiolated polysaccharide. Rehydration of crosslinked or uncrosslinked polysaccharide particles may be carried out without clumping by dispersing the particles in a biocompatible water-miscible polar dispersant such as ethanol and combining the dispersion with sufficient aqueous solvent for the particles to convert them to a cohesive hydrogel. The hydrated particles or sponge may assist in returning an injured, inflamed or surgically repaired surface to a normal state, e.g., through one or more healing mechanisms such as modulation of an inflammatory response, phagocytosis, mucosal remodeling, reciliation or other full or partial restoration of normal function.